chore: Add explicit ON DELETE CASCADE for embedded_dashboards

UPDATING.md

@@ -24,6 +24,7 @@ assists people when migrating to a new version.
 
 ## Next
 
+- [24939](https://github.com/apache/superset/pull/24939): Augments the foreign key constraints for the `embedded_dashboards` table to include an explicit CASCADE ON DELETE to ensure the relevant records are deleted when a dashboard is deleted. Scheduled downtime may be advised.
 - [24657](https://github.com/apache/superset/pull/24657): Bumps the cryptography package to augment the OpenSSL security vulnerability.
 - [24628](https://github.com/apache/superset/pull/24628): Augments the foreign key constraints for the `dashboard_owner`, `report_schedule_owner`, and `slice_owner` tables to include an explicit CASCADE ON DELETE to ensure the relevant ownership records are deleted when a dataset is deleted. Scheduled downtime may be advised.
 - [24488](https://github.com/apache/superset/pull/24488): Augments the foreign key constraints for the `sql_metrics`, `sqlatable_user`, and `table_columns` tables to include an explicit CASCADE ON DELETE to ensure the relevant records are deleted when a dataset is deleted. Scheduled downtime may be advised.

superset/daos/dashboard.py

@@ -198,7 +198,6 @@ def delete(cls, items: Dashboard | list[Dashboard], commit: bool = True) -> None
         # bulk delete, first delete related data
         for item in get_iterable(items):
             item.slices = []
-            item.embedded = []
             db.session.merge(item)
         # bulk delete itself
         try:

superset/migrations/versions/2023-08-09_15-39_4448fa6deeb1__dd_on_delete_cascade_for_embedded_dashboards.py.py

@@ -0,0 +1,48 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+"""add on delete cascade for embedded dashboards
+
+Revision ID: 4448fa6deeb1
+Revises: 2e826adca42c
+Create Date: 2023-08-09 15:39:58.130228
+
+"""
+
+# revision identifiers, used by Alembic.
+revision = "4448fa6deeb1"
+down_revision = "2e826adca42c"
+
+from superset.migrations.shared.constraints import ForeignKey, redefine
+
+foreign_keys = [
+    ForeignKey(
+        table="embedded_dashboards",
+        referent_table="dashboards",
+        local_cols=["dashboard_id"],
+        remote_cols=["id"],
+    ),
+]
+
+
+def upgrade():
+    for foreign_key in foreign_keys:
+        redefine(foreign_key, on_delete="CASCADE")
+
+
+def downgrade():
+    for foreign_key in foreign_keys:
+        redefine(foreign_key)

superset/models/embedded_dashboard.py

@@ -40,7 +40,11 @@ class EmbeddedDashboard(Model, AuditMixinNullable):
 
     uuid = Column(UUIDType(binary=True), default=uuid.uuid4, primary_key=True)
     allow_domain_list = Column(Text)  # reference the `allowed_domains` property instead
-    dashboard_id = Column(Integer, ForeignKey("dashboards.id"), nullable=False)
+    dashboard_id = Column(
+        Integer,
+        ForeignKey("dashboards.id", ondelete="CASCADE"),
+        nullable=False,
+    )
     dashboard = relationship(
         "Dashboard",
         back_populates="embedded",